He then appointed Marcian to the prefecture of the East, and gave him the conduct of the war which was now inevitable.
No sooner did the Persian monarch find his kingdom seriously menaced than, despite his advanced age, he immediately took the field in person.
Giving the command of a flying column of 6000 men to Adarman, a skilful general, he marched himself against the Romans, who under Marcian had defeated a Persian force, and were besieging Nisibis, forced them to raise the siege, and, pressing forward as they retired, compelled them to seek shelter within the walls of Daras, which he proceeded to invest with his main army.

Meanwhile Adarman, at the head of the troops entrusted to him, crossed the Euphrates near Circesium, and, having entered Syria, carried fire and sword far and wide over that fertile province.

Repulsed from Antioch, where, however, he burnt the suburbs of the town, he invaded Coelesyria, took and destroyed Apamea, and then, recrossing the great river, rejoined Chosroes before Daras.

The renowned fortress made a brave defence.

For about five months it resisted, without obtaining any relief, the entire force of Chosroes, who is said to have besieged it with 40,000 horse and 100,000 foot.